The Denholm landslide, Saskatchewan. Part I: Geology

1983 ◽  
Vol 20 (2) ◽  
pp. 197-207 ◽  
Author(s):  
E. A. Christiansen
Keyword(s):  
Shear Zone ◽  
Radiocarbon Dating ◽  
Upper Cretaceous ◽  
Average Rate ◽  
Surface Expression ◽  
Recent Time ◽  
Displacement Rate ◽  
The North ◽  
Colorado Group ◽  
Judith River Formation

The Denholm landslide, whose surface is composed of scarps, ridges, and elongated depressions, is 160 m high, 2000 m wide, and up to 100 m thick. The shear zone is in silty, montomorillonitic clay of the upper part of the Lea Park Formation and Upper Colorado Group unit. The Upper Cretaceous Judith River Formation and the Quaternary Empress, Sutherland, and Saskatoon groups were affected by the landslide. Although these sediments were fractured and gravity faulted by tension when the landslide moved, they can be readily traced through the landslide, particularly the upper part. The scarps (gravity faults), ridges (horsts), and elongated depressions (grabens) are the surface expression of tension resulting from the stretching of beds during the landslide.The movement of the landslide is thought to have started when the North Saskatchewan spillway eroded to the level of the present shear zone about 11 000 years ago (established by radiocarbon dating) and is believed to have stopped in recent time. During this time, it moved about 390 m across the North Saskatchewan River alluvium at an average rate of 35 mm per year. As the landslide moved across the valley, it encountered deposition of alluvium at an average rate of about 2.4 mm per year which resulted in the curved shear zone on the alluvium. Keywords: retrogressive landslide, shale-alluvium, displacement, rate, age.

scholarly journals FIRST RECORD OF OSTRACODS IN THE ESTIVA FORMATION (PERNAMBUCO BASIN, UPPER CRETACEOUS), NORTHEAST OF BRAZIL

2021 ◽  
Vol 31 (1) ◽  
pp. 16-26
Author(s):  
Cecília Barros ◽  
Enelise Piovesan ◽  
Mário Lima Filho ◽  
Sonia Agostinho
Keyword(s):  
Literature Review ◽  
Continental Shelf ◽  
Shear Zone ◽  
Upper Cretaceous ◽  
First Record ◽  
The State ◽  
Basin Evolution ◽  
Southern Coast ◽  
The South ◽  
The North

The present work deals with the first record of ostracods in the Estiva Formation, Pernambuco Basin (Cupe, 1 LABIO-PE1 borehole). The Pernambuco Basin extends throughout the southern coast of the state of Pernambuco and is limited by the Pernambuco Shear Zone, in the north and by the Maragogi High, in the south. The Estiva Formation consists of continental shelf carbonates dated as Upper Cretaceous. The analysis and interpretation of the data were performed through literature review, stratigraphic data surveys, and sampling. The methodology used for the treatment of the samples consisted of the following steps: collection, weighing and fragmentation of the samples; washing and drying of the calcined materials; and screening and picking of the carbonatic microfossils. Rare ostracods were found, probably belonging to the brackish genus Fossocytheridea Swain & Brown, 1964. The recognition of the ostracod fauna and its paleoecology aims to contribute to the understanding of the Pernambuco Basin evolution.

A highway cut failure in Cretaceous sediments at Maymont, Saskatchewan

1979 ◽  
Vol 16 (4) ◽  
pp. 703-715 ◽  
Author(s):  
J. Krahn ◽  
R. F. Johnson ◽  
D. G. Fredlund ◽  
A. W. Clifton
Keyword(s):  
Upper Cretaceous ◽  
Slip Surface ◽  
Crossing Over ◽  
Glacial Ice ◽  
The North ◽  
Shearing Resistance ◽  
Engineering Significance ◽  
The Stability ◽  
Shear Box ◽  
Judith River Formation

In 1973 the Saskatchewan Department of Highways began construction of a crossing over the North Saskatchewan River at Maymont, Saskatchewan. The south approach to the river required a cut some 20 m in depth at the top edge of the valley and when the excavation reached the design elevation a massive failure occurred on one of the backslopes. The major portion of the slip surface followed a slickensided clay shale zone. An analysis of the failure indicates residual angles of shearing resistance were being mobilized. The reason for mobilizing only the residual strength is attributed to previous shearing arising from glacial ice-thrusting.The sliding occurred entirely within the sediments of the nonmarine Upper Cretaceous Judith River Formation, but the strengths mobilized were essentially the same as those mobilized by slides in the marine Upper Cretaceous Bearpaw and Lea Park Formations. Negative water pressures arising from the stress change due to excavating did not appear to influence the stability. Direct shear box tests on natural slickensided surfaces gave strengths higher than required for a safety factor of unity. The testing of precut surfaces gave results that seem to correlate more closely with the field residual strengths. Furthermore, the Maymont case history clearly illustrates the need for identifying geological details and demonstrates the engineering significance of glacial ice-thrusting.

scholarly journals Crustal variability along the rifted/sheared East African margin: a review

2021 ◽  
Vol 41 (2) ◽  
Author(s):  
Maren Vormann ◽  
Wilfried Jokat
Keyword(s):  
East Africa ◽  
Shear Zone ◽  
Structural Changes ◽  
The South ◽  
East African ◽  
The North ◽  
Rifted Margins ◽  
Continental Block ◽  
Seismic Lines ◽  
Southeastern Madagascar

AbstractThe East African margin between the Somali Basin in the north and the Natal Basin in the south formed as a result of the Jurassic/Cretaceous dispersal of Gondwana. While the initial movements between East and West Gondwana left (oblique) rifted margins behind, the subsequent southward drift of East Gondwana from 157 Ma onwards created a major shear zone, the Davie Fracture Zone (DFZ), along East Africa. To document the structural variability of the DFZ, several deep seismic lines were acquired off northern Mozambique. The profiles clearly indicate the structural changes along the shear zone from an elevated continental block in the south (14°–20°S) to non-elevated basement covered by up to 6-km-thick sediments in the north (9°–13°S). Here, we compile the geological/geophysical knowledge of five profiles along East Africa and interpret them in the context of one of the latest kinematic reconstructions. A pre-rift position of the detached continental sliver of the Davie Ridge between Tanzania/Kenya and southeastern Madagascar fits to this kinematic reconstruction without general changes of the rotation poles.

scholarly journals Evidence of Unknown Paleo-Tsunami Events along the Alas Strait, West Sumbawa, Indonesia

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 46
Author(s):  
Bachtiar W. Mutaqin ◽  
Franck Lavigne ◽  
Patrick Wassmer ◽  
Martine Trautmann ◽  
Puncak Joyontono ◽  
...  
Keyword(s):  
Radiocarbon Dating ◽  
Pyroclastic Flows ◽  
Western Coast ◽  
Eastern Shore ◽  
Tsunami Deposits ◽  
The West ◽  
Marine Deposits ◽  
Sedimentary Records ◽  
The North ◽  
Large Earthquakes

Indonesia is exposed to earthquakes, volcanic activities, and associated tsunamis. This is particularly the case for Lombok and Sumbawa Islands in West Nusa Tenggara, where evidence of tsunamis is frequently observed in its coastal sedimentary record. If the 1815 CE Tambora eruption on Sumbawa Island generated a tsunami with well-identified traces on the surrounding islands, little is known about the consequences of the 1257 CE tremendous eruption of Samalas on the neighboring islands, and especially about the possible tsunamis generated in reason of a paucity of research on coastal sedimentary records in this area. However, on Lombok Island, the eruption of the Samalas volcano produced significant volumes of pyroclastic flows that entered the sea in the North and East of the island. These phenomena must have produced a tsunami that left their traces, especially on Sumbawa Island, whose western coastline is only 14 km away from Lombok’s eastern shore. Therefore, the main goal of this study is to investigate, find evidence, and determine the age of marine-origin sediments along the shore of the Alas Strait, Indonesia. We collected and analyzed samples of coral and seashells from marine deposits identified along the west coast of Sumbawa, i.e., in Belang Island and abandoned fishponds in Kiantar Village, in order to identify the sources and the occurrence period of these deposits events. Based on the radiocarbon dating of coral and seashell samples, we concluded that none of the identified marine deposits along the western coast of Sumbawa could be related chronologically to the 1257 CE eruption of Samalas. However, possible tsunami deposits located in Belang Island and abandoned fishponds in Kiantar Village yielded 4th century CE, 9th century CE, and 17th century CE. We also conclude that past large earthquakes triggered these tsunamis since no known volcanic eruption occurred near the Alas Strait at that time that may have triggered a tsunami.

scholarly journals The Dabie Extensional Tectonic System: Structural Framework

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Quanlin Hou ◽  
Hongyuan Zhang ◽  
Qing Liu ◽  
Jun Li ◽  
Yudong Wu
Keyword(s):  
Shear Zone ◽  
Shear Zones ◽  
Ultrahigh Pressure ◽  
Metamorphic Complex ◽  
The South ◽  
Magma Intrusion ◽  
The North ◽  
Extensional Tectonic ◽  
Mechanism Transition ◽  
Tectonic System

A previous study of the Dabie area has been supposed that a strong extensional event happened between the Yangtze and North China blocks. The entire extensional system is divided into the Northern Dabie metamorphic complex belt and the south extensional tectonic System according to geological and geochemical characteristics in our study. The Xiaotian-Mozitan shear zone in the north boundary of the north system is a thrust detachment, showing upper block sliding to the NNE, with a displacement of more than 56 km. However, in the south system, the shearing direction along the Shuihou-Wuhe and Taihu-Mamiao shear zones is tending towards SSE, whereas that along the Susong-Qingshuihe shear zone tending towards SW, with a displacement of about 12 km. Flinn index results of both the north and south extensional systems indicate that there is a shear mechanism transition from pure to simple, implying that the extensional event in the south tectonic system could be related to a magma intrusion in the Northern Dabie metamorphic complex belt. Two 40Ar-39Ar ages of mylonite rocks in the above mentioned shear zones yielded, separately, ~190 Ma and ~124 Ma, referring to a cooling age of ultrahigh-pressure rocks and an extensional era later.

Subsidence and sea-level rise in the Thames Estuary

1972 ◽  
Vol 272 (1221) ◽  
pp. 121-130 ◽  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Average Rate ◽  
Thames Estuary ◽  
The North ◽  
Storm Waves ◽  
Late Cretaceous Period ◽  
The North Sea ◽  
Sea Area ◽  
Cretaceous Period

The development of the area, of the Thames Estuary is briefly traced since the late Cretaceous period, with its present outline being due to a combination of factors. The overall subsidence of the North Sea area, the ‘Alpine5 fold movements, and the transgression of the sea since the retreat of the Weichselian icesheets have all contributed. The positions of the shore-line during the critical phase, 9600 b.p. to 8000 b.p., of this last transgression of the sea are shown. Subsequent to this main transgressive phase, erosion of the shoreline has been rapid due to storm-waves and tidal current action. An estimation of the average rate of subsidence and/or sea-level rise is given based on the concept of sedimentary equilibrium in which a figure of 12.7 cm (5 in) per century is arrived at.

RADIOCARBON DATING OF MESOLITHIC OPEN-AIR SITES IN THE COVERSAND AREA OF THE NORTH-WEST EUROPEAN PLAIN: PROBLEMS AND PROSPECTS

Archaeometry ◽  
2012 ◽  
Vol 55 (3) ◽  
pp. 545-562 ◽  
Author(s):  
PH. CROMBÉ ◽  
E. ROBINSON ◽  
M. VAN STRYDONCK ◽  
M. BOUDIN
Keyword(s):  
Radiocarbon Dating ◽  
North West ◽  
The North ◽  
West European
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